The proposed study will develop and test an HIV and STD prevention program for heterosexual adults of unknown or negative serostatus. Our primary goal is to reduce the incidence of sexual behaviors that place women and men at risk for HIV and other sexually transmitted diseases. At the same time, the study will identify specific determinants of sexual risk behavior, and will test the validity and relevance of our extensive modification (M-ARRM) of the AIDS risk Reduction Model. Gender- specificity of determinants will be a particular focus. Study participants will be African-American, Latina/o, and Caucasian women and men who do not currently use drugs. Elicitation studies conducted with the target population will provide data which, in conjunction with the theoretical framework, will guide the development and implementation of the culturally sensitive intervention program. In our study with women recruited from a family planning clinic in Brooklyn, we will conduct a randomized clinical trial and will systematically evaluate dosage effects of 8- and 4-session intervention programs of comparable content but varying depth, relative to a waiting-list control condition. In our study with men, obtained partly via peer nominations from women at the same site and partly from an STD clinic, we will conduct a qualitative, exploratory investigation in order to identify gender-specific barriers to sexual behavior change and potential strategies for developing interventions for heterosexual men.